Self-propelled machines, such as lawn mowing machines and the like, often provide handles on which controls are mounted for engagement and/or manipulation by operators or users of such machines. In particular, a “walk behind” type, self-propelled mowing machine typically has a handle extending behind a power plant or other main operative assembly of the machine for gripping by an operator as the operator walks behind the machine during movement thereof in a forward direction. Typically, one or more controls are mounted toward the end of the handle in a convenient location for the user to manipulate while gripping the handle and operating the machine. One such control is the operator presence control or “dead man” control, which generally includes a spring-biased handle which can be grasped by the operator during normal operation of the machine to enable the motor of the machine. If the operator presence control handle is thereafter released, the machine action is rapidly terminated for reasons of safety. Another well-known control is the speed control, which for self-propelled mowing machines is generally connected to a variable speed transmission associated with the engine and controls the speed of the self-propelled traction wheels. These speed controls typically comprise a lever pivotally mounted onto the machine handle such that the speed of the self-propulsion can be controlled by moving the lever back and forth, which often requires the operator to remove one hand from the handle in order to operate the speed control. These independent systems also typically require the operator to control two or more separate functions while operating the machine. Unfortunately, recent marketing research indicates that many consumers of self-propelled machines would prefer a minimum number of control mechanisms requiring manipulation during operation of such machines in order to simplify use of the machines.
Many examples exist of conventional machines that utilize multiple separate controls during the engagement and running of the machine. U.S. Pat. No. 4,281,732 to Hoch discloses a lawn mower with a control mechanism for a propelled-drive clutch wherein the control mechanism includes a dead-man control lever which operates to hold a clutch-control lever in a clutch-engage position only when the dead-man control lever is held in a lever holding position. The lawn mower is operated in a manner that upon release of the dead-man control lever, the dead-man control lever automatically moves to a lever-release position which permits the clutch-control lever to automatically move to a clutch-disengaged position. U.S. Pat. No. 4,309,862 to Carlson discloses an operator presence control belt that holds in place a throttle control lever wherein the throttle control lever can be moved forward after the operator presence control belt is engaged. A spring loaded detent on the end of the operator presence control belt holds the throttle control lever in an engaged position until the operator presence control is released such that the throttle lever and operator presence control are interlocked.
U.S. Pat. No. 4,327,539 to Bricko et al. discloses the use of a single belt to operate both the drive system and the clutch system for outdoor power equipment. The belt is first rotated counter clockwise to cause a hook to catch on a finger of the drive lever, then as the belt is rotated in a clockwise direction the hook causes the drive lever to rotate and a pin engages a recess in the clutch lever to cause the clutch to engage. Yet another patent related to prior operator presence control and drive systems is U.S. Pat. No. 4,466,232 to Beugelsdyk et al. which discloses a compact safety control assembly for lawnmowers having a cable actuated clutch between the motor and the blade which includes a dead-man function along with a operating mechanism requiring two distinct steps for engaging the clutch and initiating rotation of the lawnmower blade.
Twist-grip throttle control systems have been used for years in the motorcycle-like vehicle and outboard marine engine fields. For example, U.S. Pat. No. 4,019,402 to Leonheart discloses a motorcycle throttle twist-grip control unit that is connected by a Bowden cable to the carburetor of the motorcycle. Likewise, U.S. Pat. No. 4,133,193 to Sanada et al. discloses a throttle grip locking device of a motorcycle having at one end of a handle a rotary throttle grip to control the operation of the engine wherein, when the engine is stopped, the throttle grip would be locked so as to be non-rotatable. U.S. Pat. No. 4,191,065 to Golobay et al. discloses a twistable type throttle grip assembly especially adapted for use with motorcycle-like vehicles wherein the throttle grip assembly manipulates a single control cable and is normally operational in a first rotational range for controlling the supply of fuel to the vehicles internal combustion engine thereby controlling the vehicle speed.
Regarding the outboard marine motor field, U.S. Pat. No. 5,545,064 to Tsunekawa et al. discloses a throttle and transmission control assembly adapted to be mounted on the tiller of an outboard motor for controlling its transmission and throttle wherein both the transmission and throttle controls employ devices that convert rotary into reciprocating motion and which amplify the reciprocating motion so as to permit a compact assembly. U.S. Pat. No. 6,093,066 to Isogawa et al. describes an outboard motor throttle and transmission control that employs a Bowden wire mechanism for transmitting control signals from the tiller handle to the engine throttle and transmission control. A twist-grip throttle control and a pivotally supported transmission control are mounted on a tiller arm and are connected by a Bowden wire actuating mechanism to the respective components of an outboard motor. Finally, U.S. patent application No. US2001/0046819 to Kawai et al. discloses an outboard motor featuring a compact throttle control and transmission shifting control on a handle connected to a tiller. The throttle control mechanism includes a twist-grip throttle control that is connected to a throttle control shaft that is journalled by a first bearing and a second bearing in a suitable manner for changing the speed of the engine.
Therefore, it would advantageous to employ a variable speed twist control that is operatively connected to a variable speed transmission of a self-propelled mowing machine to control the speed of propulsion. The twist control can allow for various hand positions for ease of operation and can be used in conjunction with an operator presence control for engine control and engagement of the speed system.